Impedance matching tap-off coupler for coaxial transmission lines, having integral variable capacitance



June 1967 YUKiO FUJIMOTO 3,324,421

IMPEDANCE MATCHING TAP-OFF COUPLER FOR COAXIAL TRANSMISSION LINES, HAVING INTEGRAL VARIABLE CAPACITANCE Filed Oct. 19, 1964 2 Sheets-Sheet 1 INVEN R. Mai m June 1967 YUKIO FUJIMOTO 3,324,421

IMPEDANCE MATCHING TAP-OFF COUPLER FOR CUAXIAL TRANSMISSION LINES, HAVING INTEGRAL VARIABLE CAPACITANCE Filed on. 19, 1964 2 Sheets-Sheet I i w INVENTOR.

United States Patent 3 324 421 IMPEDANQE MATCH-ENG TAP-OFF COUPLER FOR OUAXHAL TRANSMESTGN LINES, HAVING IN- VARHABLE CAPACITANCE Ynkio Fujimoto, Fujisawa-shi, Japan, assignor to Mrharu Tsushinkilri 60., Ltd, Tokyo, .iapan, a corporation of Japan Filed Oct. 1?, 1964, Ser. No. 464,811 6 Claims. (6i. 3339) AESTRAQT 9F THE DTSCLOURE A tap-01f coupler for coaxial transmission lines with electrical connections through piercing pins and having a cylindrically shaped metal capacitor plate in one adjustable part into which the rear end of one of the piercing pins is adjustably moved axially therein to vary the impedance for matching.

The present invention relates to an impedance matching tap-off coupled for coaxial transmission lines, comprising an inner conductor and an outer conductor, the two being separated by suitable insulation.

Heretofore, in the reception of television transmission, especialiy with a multiple outlet system, a tap was made on the main coaxial line to transfer energy to the branch lines.

Experiments conducted to achieve desirable results in the adjustment of the couplers impedance have usually been unsuccessful.

It is one object of the present invention to provide an impedance matching highly efiicient tap-off coupler for coaxial transmission lines which can easily and quickly be installed onto a coaxial cable, and impedance of which can be adjusted.

It is another object of the present invention to provide an impedance matching tap-off coupler for coaxial transmission lines comprising four separate parts; the upper two conductor parts are designed to encircle and firmly grip the main coaxial cable. Two short pins in the lower conductor part pierce the outer insulating coating of the coaxial cable, thereby making connection with the outer conductor of the cable. The lower conductor is formed with an internally threaded opening in which is connected an externally threaded member which constitutes the third part and which is comprised of an outer conducting portion and an inner conductor which includes a piercing pin. The outer conducting portion and the inner conductor are fully insulated from each other, and are firmly held together with the insulation. The lower portion of the inner conductor of the third part projects into an aperture in the lower portion of the third part into which a cartridge (the fourth part) is fitted. The cartridge has an insulated outer conducting portion and an inner conductor which forms an impedance element. The inner conductor of the cartridge comprises a cylindrical metal part (or a variable resistor). The cylindrical metal part and the outer conducting portion of the cartridge constitute a capacitor. The third part is fitted onto the fourth part and the lower portion of the inner conductor of the third part is fitted into the cylindrical metal part and the upper portion of the cartridge. The cylindrical metal part of the cartridge is located inside of the outer conducting portion of the third part, and the degree 3,324,421 Patented June 6, 1957 of insertion of the lower portion of the inner conductor of the third part into the cylindrical metal part of the inner conductor of the cartridge constitutes a variable capacitor. The impedance of the coupler is adjusted by the changes in the capacitance.

When a variable resistor is used for the impedance element, the degree of insertion of the cartridge into the third part determines the resistance value, providing the means for adjusting the impedance.

With these and other objects in view which will become apparent in the following detailed description, the present invention will be clearly understood in connection with the accompanying drawings, in which:

FIGURE 1 is a front elevation of an impedance matching tap-off coupler according to the present invention;

FIG. 2 is an end elevation of the tap-off coupler of FIG. 1 with a main coaxial cable attached thereto;

FIG. 3 is a section along the lines AA of FIG. 1;

FIG. 3a is an axial sectional view of the third part and the cartridge of the tap-off coupler showing an insulated piercing pin;

PEG. 4 is an electrical transmission circuit of the tapoff coupler illustrated in FIGS. 13;

FIG. 5-1 is an axial sectional view of a third part and a cartridge, showing a modified construction;

FIG. 5-11 is an electrical transmission circuit of the coupler illustrated in FIG. 5-I;

FIG. 6-1 is an axial sectional view of a third part and a cartridge, showing another modified construction; and

FIG. 6H is an electrical transmission circuit of the coupler illustrated in FIG. 6-I.

Referring now to the drawings, and more particularly to FIG. 13, an impedance matching tap-ofi coupler according to the present invention comprises a lower conductor 2 having a semi-circular groove 3 and an indented V-shaped recess 4 on the inside.

The diameter of the groove 3 matches the diameter of a coaxial main cable 24. The tap-off coupler further comprises an upper conductor 5 having a semi-circular groove 6 and a V-shaped protruding part 7 on the inside.

The protruding part 7 fits snugly in the V-shaped recess 4, and the coaxial cable 24 fits snugly inside the semicircular grooves 3 and 6, which form a cylindrical opening when the two conductors 2 and 5 are fitted together. When the coaxial cable 24 is inserted into the cylindrical grooves (3 and 6), pins 8 protruding out into the groove 3 from the lower conductor 2 (FIG. 3) pierce through the outer insulating coating 25 of the coaxial cable 24 and connect with outer conductor 26 of the coaxial cable.

The lower conductor 2 has an opening 28 having internal threads 2'7 which receive an externally threaded third part 9. The lower conductor 2 and the third part 9 are made of conducting materials to obtain an electrical connection between the outer conductor 26 of the coaxial cable 24 and the conducting material of the third part 9, through the piercing pins 8 and the body of the lower conductor 2. The lower outside portion of the third part 9 is formed into the shape of a nut 1t) and has an annular aperture 11 having internal threads 12. A piercing pin 13 having an inner protruding metal end 14 is disposed in the interior of the third part 9, which is covered tightly with insulation 15. The inner protruding metal end 14 is fitted and positioned into the aperture 11.

The piercing pin 13 has an outer extending portion of length slightly longer than the radius of the cable 24.

3 As illustrated in FIG. 3, the outer conductor 26 is cut away at its outer coating at the desired position of the cable to be engaged before the third part 9 is engaged into the opening 28, and the head 13 of the piercing pin pierces the inner insulation and connects with the inner conductor 29 of the cable 24. As shown in FIG. 3a where the piercing pin 13 has an insulation covering 13" around its extending portion (except the pointed head 13'), it may be unnecessary to cut away a portion of the outer conductor of the cable.

A cartridge 20 with an external thread 16 is placed in the internally threaded aperture 11 of the third part 9. The cartridge 20 also includes a cylindrical metal part 18 and a connector 19 tightly covered with insulation 21. The connector 19 has a slit on the end opposite the metal part 18. The lower portion of the cartridge 20 has external threads 22, which are attached to a branch cable (not shown) in a conventional way. The cartridge 20 possesses a predetermined capacitance between the metal part 18 and the outer conducting portion of the cartridge 20. When the cartridge 20 is'fitted into the aperture 11 of the third part 9, the cylindrical metal part '18 encircles the inner protruding metal end 14 together with its outer insulation 15, whereby a further capacitance arises between the two metal parts 14 and 18.

The capacitance between parts 14 and 18 can be adjusted according to the degree of insertion of the inner protruding metal end 14 into the cylindrical opening of the metal part 18. That is, as indicated in FIG. 4, the cylindrical metal part 18 of the cartridge 20 possesses a capacitance C between the metal part 18 and the outer conducting portion of the cartridge 20 and by placing the cartridge 20 in the aperture 11 of the third part 9; and by placing the inner protruding metal end 14 inside the cylindrical opening of the metal part 18, a variable capacitor C is formed.

On the external threads 16 on the upper portion of the cartridge 20, a suitable stop, such as a nut 23, is located to secure the cartridge 20. For attaching the coupler to the cable 24 and securing it at the desired position, a bolt 30 and a nut 31 are provided, as illustrated in FIG. 1.

As clearly illustrated in FIG. 3, the pointed short pins 8 protrude slightly into the groove 3 of the lower conductor 2 to pierce through the outer insulation 25 of the cable 24 and connect with the outer conductor 26 of the cable 24. These pins are intended to provide a good electrical connection between the lower conductor 2 and the outer conductor 26 of the cable 24 as well as to firmly secure the cable in the grooves 3 and 6. The piercing pin 13 extends through the cut in the cable 24, and pierces the inner insulation and connects with the inner conductor 29 of the cable 24 when the third part 9 is threadedly engaged in the opening 28 of the lower conductor 2.

When the piercing pin 13 includes an insulation covering 13 (-FIG. 3a) about its outer projecting portion (except at the pointed head 13'), the pin 13 may be pierced into the cable without any cut formed therein, because electrical connection between the pin 13 and the outer conductor 26 of the cable 24 cannot occur and a short circuit cannot result.

The tap-oif coupler constructed according to the present invention with operations as described above, may be adjusted by adjustably securing the cartridge 20 relative the third part 9 in a suitable position where the desired value of the capacitance is obtained. The capacitance value, as shown at C in FIG. 4, depends upon the degree of insertion of the cartridge 20 into the third part 9. Accordingly, this tap-ofi coupler contains two impedance elements C and C when in use. Therefore, a coupling loss suitable for a tap-oft" point on the cable to which the coupler is attached may be selected by adjusting the proper values of the elements.

With an increase in the coupling loss of the tap-off coupler, the difference of loss in the lower and high frequency TV band decreases, and with a decrease in the coupling loss of the tap-oh" coupler, the difference of loss in the low and high frequency TV band increases. It is one of the special characteristics of the present invention to utilize this frequency quality.

In the past, impedance elements such as capacitance or resistors were invariable. However, the tap-off coupler of the present invention has two capacitances, one or both of which are variable, as described herein. Capacitance between the cylindrical metal part 18 (containing an inner conductor of the cartridge 2) and the inner protruding metal end 14 (constituting an inner conductor of the third part 9) is changed in proportion to the degree of insertion of the cartridge 20 into the third part 9. Deep insertion makes the capacitance large, because the coupling loss is small, whereas a slight insertion makes the capacitance small, because the coupling loss is large.

Referring now again to the drawings, and more particularly to FIGS. 5-6, there are illustrated modified embodiments of the cartridge of the present invention. FIG. 5I shows a cartridge 20 comprising a cylindrical metal part 18 as an inner conductor, the metal part 18' being held with a threaded shaft 30 in an aperture of the cartridge 20. The shaft 30 may be rotated by a suitable tool such as a screw-driver, the position of the metal part 18' thereby being axially changed. The electrical circuit diagram of this embodiment is illustrated in FIG. 5-II, where two variable capacitors are established as impedance elements. In this case the value of the capacitance C is also variable because of the relationship between the metal part 18' and the outer conducting portion of the cartridge 20.

FIGS. 6-1 and 6II show another embodiment where the capacitance of the impedance elements is changed and a variable resistor R is used. This is accomplished by using the inner protruding metal end 14 of the third part 9' as a variable terminal. By the degree of insertion of the cartridge 20 into the third part 9', the resistance value of the variable resistor R is adjusted.

While I have disclosed several embodiments of the present invention, it is to be understood that these embodiments are given by example only and not in a limiting sense, the scope of the present invention being determined by the objects and the claims.

I claim:

1. An impedance matching tap-otf coupler for transmitting electrical energy from a main coaxial cable having an inner conductor, an outer conductor, and an inner insulation therebetween and an outer insulating coating about the outer conductor, comprising two clamping conductors, each having a semi-circular groove for together firmly engaging in said grooves said main coaxial cable,

short pins for piercing through said outer insulating coating of said cable so as to connect with said outer conductor of said cable,

said short pins protruding out from one of said clamping conductors into one of said semi-circular grooves,

said one of said clamping conductors having an internally threaded opening axially intersecting said one of said semi-circular grooves,

a third part having an outer conducting portion and having first external threads engaging with said one of said clamping means at said threaded opening,

said third part including an inner conductor spaced from said outer conducting portion and comprising a piercing pin extending from an inner protruding metal end to an outer extending portion,

said outer extending portion of a length being slightly more than the radius of said cable and piercing said cable and said inner insulation and adapted to connect to said inner conductor of said cable,

insulation material disposed between said piercing pin and said outer conducting portion of said third part,

and spaced from said outer conducting portion about said inner protruding metal end to define thereat an annular aperture,

a cartridge adjustably fitting into said annular aperture,

said cartridge comprising a second outer conducting portion having second external threads and adapted for adjustable attachment to said outer conducting portion of said third part in said annular aperture,

said cartridge adapted for attachment with a branch cable,

said cartridge including a second inner conductor insulated from said second outer conducting portion,

said second inner conductor comprising a cylindrical metal part and a connector,

said second outer conducting portion and said cylindrical metal part constituting a capacitor,

said inner protruding metal end disposed inside said cylindrical metal part constituting a variable capacitor, and

the degree of insertion of said inner protruding metal end into said cylindrical metal part being adjustable by said adjustable attachment of said cartridge to said outer conducting portion of said third part, thereby determining the value of the capacity of said variable capacitor.

27 An impedance matching tap-ofi coupler for transmitting electrical energy from a main coaxial cable having an inner conductor, an outer conductor, an inner insulation therebetween and an outer insulating coating about the outer conductor, comprising two clamping conductors, each having a semi-circular groove for together firmly engaging in said grooves said main coaxial cable,

short pins for piercing through said outer insulating coating of said cable so as to connect with said outer conductor of said cable,

said short pins protruding out from one of said clamping conductors into one of said semi-circular grooves,

said one of said clamping conductors having an internally threaded opening axially intersecting said one of said semi-circular grooves,

a third part having an outer conducting portion and having first external threads engaging with said one of said clamping means at said threaded opening,

said third part including an inner conductor spaced from said outer conducting portion and comprising a piercing pin extending from an inner protruding metal end to an outer extending portion terminating with a pointed head,

said outer extending portion of a length slightly more than the radius of said cable and piercing said cable and said inner insulation and adapted to connect to said inner conductor of said cable,

insulation material disposed between said piercing pin and said outer conducting portion of said third part and spaced from said outer conducting portion about said inner protruding metal end to define thereat an annular aperture,

said annular aperture being internally threaded on said outer conducting portion,

a cartridge comprising a second outer conducting portion having second external threads,

said cartridge adjustably engaging with said second external threads, said internally threaded outer conducting portion of said third part thereby adjustably fitting into said annular aperture,

said cartridge including third external threads for attachment with a branch cable,

said cartridge including a second inner conductor insulated from said second outer conducting portion,

said second inner conductor comprising a cylindrical metal part and a connector,

said second outer conducting portion and said cylindrical metal part constituting a capacitor,

said inner protruding metal end disposed inside said cylindrical metal part constituting a variable capacitor, and

the degree of insertion of said inner protruding metal end into said cylindrical metal part being adjustable by said adjustable attachment of said cartridge to said outer conducting portion of said third part, thereby determining the value of the capacity of sa1d variable capacitor.

3. The coupler, as set forth in claim 2, further comprising stop means mounted on said second external threads or" said cartridge to secure said cartridge at any desired position for obtaining a desirable capacitance between said third part and said cartridge.

4. The coupler, as set forth in claim 2, wherein said piercing pin is insulated at said outer extending portion except at said pointed head,

5. The coupler, as set forth in claim 2, wherein Said second inner conductor comprises a threaded shaft,

said cylindrical metal part having a threaded opening and being threadedly engaged therein by sa1d threaded shaft,

said cartridge defining a cartridge aperture,

said cylindrical metal part disposed in said cartridge aperture, and B said shaft adapted for rotation whereby the position or said cylindrical metal part is axially adjusted.

6. A tap-ofi coupler for transmitting electrical energy from a main coaxial cable having an inner conductor, an outer conductor, an inner insulation therebetween and an outer insulating coating about the outer conductor, comprising two clamping conductors, each having a semi-circular groove for together firmly engaging in said grooves said main coaxial cable,

short pins for piercing through said outer insulating coating of said cable so as to connect with said outer conductor of said cable,

said short pins protruding out from one of said clamping conductors into one of said semiircular grooves,

said one of said clamping conductors having an internally threaded opening axially intersecting said one of said semi-circular grooves,

a third part having an outer conducting portion and having first external threads engaging with said one of said clamping means at said threaded opening,

said third part including an inner conductor spaced from said outer conducting portion and comprising a piercing pin extending from an inner protruding metal end to an outer extending portion.

said outer extending portion of a length slightly more than the radius of said cable and piercing said cable and said inner insulation and adapted to connect to said inner conductor of said cable,

insulation material disposed between said piercing pin and said outer conducting portion of said third part, and spaced from said outer conducting portion about said inner protruding metal end to define thereat an annular aperture,

a cartridge adjustably fitting into said annular aperture,

said cart-ridge comp-rising a second outer conducting portion having second external threads and adapted for adjustable attachment to said out-er conducting portion of said third part in said annular aperture,

said cartridge adapted for attachment with a branch cable,

said cartridge including a second inner conductor insulated from said second outer conducting portion,

said second inner conductor comprising a resistor and a connector,

said second outer conducting portion and said connector constituting a capacitor,

said inner protruding metal end slidably connected to said resistor constituting therewith a variable resister, and

the connecting position of said resistor with said inner rotrudiru metal end being adjustable with the degree of insertion by said adjustable attachment of said cartridge into said outer conducting portion of said third part, thereby determining the value of the resistance of said variable resistor.

References Cited UNITED STATES PATENTS Cork et a1 33333 X Cork et al 33333 X Edlen et a1. 333-97 X Edlen et al. 33397 X Maher 333-97 X ELI LIEBERMAN, Primary Examiner. 10 R. COHN, P, L. GENSLER, Assistant Examiners. 

1. AN IMPEDANCE MATCHING TAP-OFF COUPLER FOR TRANSMITTING ELECTRICAL ENERGY FROM A MAIN COAXIAL CABLE HAVING AN INNER CONDUCTOR, AN OUTER CONDUCTOR, AND AN INNER INSULATION THEREBETWEEN AND AN OUTER INSULATING COATING ABOUT THE OUTER CONDUCTOR, COMPRISING TWO CLAMPING CONDUCTORS, EACH HAVING A SEMI-CIRCULAR GROOVE FOR TOGETHER FIRMLY ENGAGING IN SAID GROOVES SAID MAIN COAXIAL CABLE, SHORT PINS FOR PIERCING THROUGH SAID OUTER INSULATING COATING OF SAID CABLE SO AS TO CONNECT WITH SAID OUTER CONDUCTOR OF SAID CABLE, SAID SHORT PINS PROTRUDING OUT FROM ONE OF SAID CLAMPING CONDUCTORS INTO ONE OF SAID SEMI-CIRCULAR GROOVES, SAID ONE OF SAID CLAMPING CONDUCTORS HAVING AN INTERNALLY THREADED OPENING AXIALLY INTERSECTING SAID ONE OF SAID SEMI-CIRCULAR GROOVES, A THIRD PART HAVING AN OUTER CONDUCTING PORTION AND HAVING FIRST EXTERNAL THREADS ENGAGING WITH SAID ONE OF SAID CLAMPING MEANS AT SAID THREADED OPENING, SAID THIRD PART INCLUDING AN INNER CONDUCTOR SPACED FROM SAID OUTER CONDUCTING PORTION AND COMPRISING A PIERCING PIN EXTENDING FROM AN INNER PROTRUDING METAL END TO AN OUTER EXTENDING PORTION, SAID OUTER EXTENDING PORTION OF A LENGTH BEING SLIGHTLY MORE THAN THE RADIUS OF SAID CABLE AND PIERCING SAID CABLE AND SAID INNER INSULATION AND ADAPTED TO CONNECT TO SAID INNER CONDUCTOR OF SAID CABLE, INSULATION MATERIAL DISPOSED BETWEEN SAID PIERCING PIN AND SAID OUTER CONDUCTING PORTION OF SAID THIRD PART, AND SPACED FROM SAID OUTER CONDUCTING PORTION ABOUT SAID INNER PROTRUDING METAL END TO DEFINE THEREAT AN ANNULAR APERTURE, A CARTRIDGE ADJUSTABLY FITTING INTO SAID ANNULAR APERTURE, SAID CARTRIDGE COMPRISING A SECOND OUTER CONDUCTING PORTION HAVING SECOND EXTERNAL THREADS AND ADAPTED FOR ADJUSTABLE ATTACHMENT TO SAID OUTER CONDUCTING PORTION OF SAID THIRD PART IN SAID ANNULAR APERTURE, SAID CARTRIDGE ADAPTED FOR ATTACHMENT WITH A BRANCH CABLE, SAID CARTRIDGE INCLUDING A SECOND INNER CONDUCTOR INSULATED FROM SAID SECOND OUTER CONDUCTING PORTION, SAID SECOND INNER CONDUCTOR COMPRISING A CYLINDRICAL METAL PART AND A CONNECTOR, SAID SECOND OUTER CONDUCTING PORTION AND SAID CYLINDRICAL METAL PART CONSTITUTING A CAPACITOR, SAID INNER PROTRUDING METAL END DISPOSED INSIDE SAID CYLINDRICAL METAL PART CONSTITUTING A VARIABLE CAPACITOR, AND THE DEGREE OF INSERTION OF SAID INNER PROTRUDING METAL END INTO SAID CYLINDRICAL METAL PART BEING ADJUSTABLE BY SAID ADJUSTABLE ATTACHMENT OF SAID CARTRIDGE TO SAID OUTER CONDUCTING PORTION OF SAID THIRD PART, THEREBY DETERMINING THE VALUE OF THE CAPACITY OF SAID VARIABLE CAPACITOR. 